"Let me apologize to anybody and everybody within our listening and reading areas. I'm very sorry for missing the two votes," Mr. Manchin said during a conference call with reporters, according to MetroNews of West Virginia.
Mr. Manchin, a Democrat and former West Virginia governor, won a special election to fill the unexpired term of the late Sen. Robert C. Byrd. He previously had indicated he was opposed to both bills.
In his conference call, Mr. Manchin told reporters he had entered a note into the Congressional Record that he would be absent during that time period.
"I didn't want anybody to think that I wouldn't make a vote or had intentionally missed a vote because it was a controversial issue," he said.
"I think that anybody who knows me ... making decisions has not been hard for me."